I think your argument would be better if you don't just say "the product would be better with more people working on it", but also say how you plan to recruit them, what you need to do that, and how velocity would increase. If you can show that you have thought it out and you can manage the product side of things, it shows that you are serious about growing the product team, not just randomly throwing capricious (and costly) demands.

Regarding the possibility of quitting, I think it's better to warn the CEO early about that, than making a decision and suddenly tell him that you are leaving. If you were the CEO, how would you want your coder/product guy to behave? Then behave like that.